The detection of adequate power supply voltage upon equipment power up requires an accurate and consistent determination of the earliest point of adequate power supply voltages, and minimization of false signals and changes the threshold at which a signal is produced indicating the proper supply potential. Previous power-on detection circuits which produce under-voltage lock-out signals for inadequate power supply voltage have almost universally relied upon comparison of an input voltage to a Zener diode reference element. However, the actual potential of the Zener diode reference is notoriously process and temperature dependent. As a result, the change in Zener potential due to manufacturing and temperature variances significantly affect product yield. Alternately, construction of discrete under-voltage lock-out circuits having selected Zener diodes is both time consuming and expensive.